Version:  2.0.40 2.2.26 2.4.37 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4

Linux/mm/mremap.c

  1 /*
  2  *      mm/mremap.c
  3  *
  4  *      (C) Copyright 1996 Linus Torvalds
  5  *
  6  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
  7  *      (C) Copyright 2002 Red Hat Inc, All Rights Reserved
  8  */
  9 
 10 #include <linux/mm.h>
 11 #include <linux/hugetlb.h>
 12 #include <linux/shm.h>
 13 #include <linux/ksm.h>
 14 #include <linux/mman.h>
 15 #include <linux/swap.h>
 16 #include <linux/capability.h>
 17 #include <linux/fs.h>
 18 #include <linux/swapops.h>
 19 #include <linux/highmem.h>
 20 #include <linux/security.h>
 21 #include <linux/syscalls.h>
 22 #include <linux/mmu_notifier.h>
 23 #include <linux/sched/sysctl.h>
 24 #include <linux/uaccess.h>
 25 #include <linux/mm-arch-hooks.h>
 26 
 27 #include <asm/cacheflush.h>
 28 #include <asm/tlbflush.h>
 29 
 30 #include "internal.h"
 31 
 32 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
 33 {
 34         pgd_t *pgd;
 35         pud_t *pud;
 36         pmd_t *pmd;
 37 
 38         pgd = pgd_offset(mm, addr);
 39         if (pgd_none_or_clear_bad(pgd))
 40                 return NULL;
 41 
 42         pud = pud_offset(pgd, addr);
 43         if (pud_none_or_clear_bad(pud))
 44                 return NULL;
 45 
 46         pmd = pmd_offset(pud, addr);
 47         if (pmd_none(*pmd))
 48                 return NULL;
 49 
 50         return pmd;
 51 }
 52 
 53 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
 54                             unsigned long addr)
 55 {
 56         pgd_t *pgd;
 57         pud_t *pud;
 58         pmd_t *pmd;
 59 
 60         pgd = pgd_offset(mm, addr);
 61         pud = pud_alloc(mm, pgd, addr);
 62         if (!pud)
 63                 return NULL;
 64 
 65         pmd = pmd_alloc(mm, pud, addr);
 66         if (!pmd)
 67                 return NULL;
 68 
 69         VM_BUG_ON(pmd_trans_huge(*pmd));
 70 
 71         return pmd;
 72 }
 73 
 74 static pte_t move_soft_dirty_pte(pte_t pte)
 75 {
 76         /*
 77          * Set soft dirty bit so we can notice
 78          * in userspace the ptes were moved.
 79          */
 80 #ifdef CONFIG_MEM_SOFT_DIRTY
 81         if (pte_present(pte))
 82                 pte = pte_mksoft_dirty(pte);
 83         else if (is_swap_pte(pte))
 84                 pte = pte_swp_mksoft_dirty(pte);
 85 #endif
 86         return pte;
 87 }
 88 
 89 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 90                 unsigned long old_addr, unsigned long old_end,
 91                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
 92                 unsigned long new_addr, bool need_rmap_locks)
 93 {
 94         struct address_space *mapping = NULL;
 95         struct anon_vma *anon_vma = NULL;
 96         struct mm_struct *mm = vma->vm_mm;
 97         pte_t *old_pte, *new_pte, pte;
 98         spinlock_t *old_ptl, *new_ptl;
 99 
100         /*
101          * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
102          * locks to ensure that rmap will always observe either the old or the
103          * new ptes. This is the easiest way to avoid races with
104          * truncate_pagecache(), page migration, etc...
105          *
106          * When need_rmap_locks is false, we use other ways to avoid
107          * such races:
108          *
109          * - During exec() shift_arg_pages(), we use a specially tagged vma
110          *   which rmap call sites look for using is_vma_temporary_stack().
111          *
112          * - During mremap(), new_vma is often known to be placed after vma
113          *   in rmap traversal order. This ensures rmap will always observe
114          *   either the old pte, or the new pte, or both (the page table locks
115          *   serialize access to individual ptes, but only rmap traversal
116          *   order guarantees that we won't miss both the old and new ptes).
117          */
118         if (need_rmap_locks) {
119                 if (vma->vm_file) {
120                         mapping = vma->vm_file->f_mapping;
121                         i_mmap_lock_write(mapping);
122                 }
123                 if (vma->anon_vma) {
124                         anon_vma = vma->anon_vma;
125                         anon_vma_lock_write(anon_vma);
126                 }
127         }
128 
129         /*
130          * We don't have to worry about the ordering of src and dst
131          * pte locks because exclusive mmap_sem prevents deadlock.
132          */
133         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
134         new_pte = pte_offset_map(new_pmd, new_addr);
135         new_ptl = pte_lockptr(mm, new_pmd);
136         if (new_ptl != old_ptl)
137                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
138         arch_enter_lazy_mmu_mode();
139 
140         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
141                                    new_pte++, new_addr += PAGE_SIZE) {
142                 if (pte_none(*old_pte))
143                         continue;
144                 pte = ptep_get_and_clear(mm, old_addr, old_pte);
145                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
146                 pte = move_soft_dirty_pte(pte);
147                 set_pte_at(mm, new_addr, new_pte, pte);
148         }
149 
150         arch_leave_lazy_mmu_mode();
151         if (new_ptl != old_ptl)
152                 spin_unlock(new_ptl);
153         pte_unmap(new_pte - 1);
154         pte_unmap_unlock(old_pte - 1, old_ptl);
155         if (anon_vma)
156                 anon_vma_unlock_write(anon_vma);
157         if (mapping)
158                 i_mmap_unlock_write(mapping);
159 }
160 
161 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
162 
163 unsigned long move_page_tables(struct vm_area_struct *vma,
164                 unsigned long old_addr, struct vm_area_struct *new_vma,
165                 unsigned long new_addr, unsigned long len,
166                 bool need_rmap_locks)
167 {
168         unsigned long extent, next, old_end;
169         pmd_t *old_pmd, *new_pmd;
170         bool need_flush = false;
171         unsigned long mmun_start;       /* For mmu_notifiers */
172         unsigned long mmun_end;         /* For mmu_notifiers */
173 
174         old_end = old_addr + len;
175         flush_cache_range(vma, old_addr, old_end);
176 
177         mmun_start = old_addr;
178         mmun_end   = old_end;
179         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
180 
181         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
182                 cond_resched();
183                 next = (old_addr + PMD_SIZE) & PMD_MASK;
184                 /* even if next overflowed, extent below will be ok */
185                 extent = next - old_addr;
186                 if (extent > old_end - old_addr)
187                         extent = old_end - old_addr;
188                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
189                 if (!old_pmd)
190                         continue;
191                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
192                 if (!new_pmd)
193                         break;
194                 if (pmd_trans_huge(*old_pmd)) {
195                         int err = 0;
196                         if (extent == HPAGE_PMD_SIZE) {
197                                 VM_BUG_ON_VMA(vma->vm_file || !vma->anon_vma,
198                                               vma);
199                                 /* See comment in move_ptes() */
200                                 if (need_rmap_locks)
201                                         anon_vma_lock_write(vma->anon_vma);
202                                 err = move_huge_pmd(vma, new_vma, old_addr,
203                                                     new_addr, old_end,
204                                                     old_pmd, new_pmd);
205                                 if (need_rmap_locks)
206                                         anon_vma_unlock_write(vma->anon_vma);
207                         }
208                         if (err > 0) {
209                                 need_flush = true;
210                                 continue;
211                         } else if (!err) {
212                                 split_huge_page_pmd(vma, old_addr, old_pmd);
213                         }
214                         VM_BUG_ON(pmd_trans_huge(*old_pmd));
215                 }
216                 if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
217                                                       new_pmd, new_addr))
218                         break;
219                 next = (new_addr + PMD_SIZE) & PMD_MASK;
220                 if (extent > next - new_addr)
221                         extent = next - new_addr;
222                 if (extent > LATENCY_LIMIT)
223                         extent = LATENCY_LIMIT;
224                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
225                           new_vma, new_pmd, new_addr, need_rmap_locks);
226                 need_flush = true;
227         }
228         if (likely(need_flush))
229                 flush_tlb_range(vma, old_end-len, old_addr);
230 
231         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
232 
233         return len + old_addr - old_end;        /* how much done */
234 }
235 
236 static unsigned long move_vma(struct vm_area_struct *vma,
237                 unsigned long old_addr, unsigned long old_len,
238                 unsigned long new_len, unsigned long new_addr, bool *locked)
239 {
240         struct mm_struct *mm = vma->vm_mm;
241         struct vm_area_struct *new_vma;
242         unsigned long vm_flags = vma->vm_flags;
243         unsigned long new_pgoff;
244         unsigned long moved_len;
245         unsigned long excess = 0;
246         unsigned long hiwater_vm;
247         int split = 0;
248         int err;
249         bool need_rmap_locks;
250 
251         /*
252          * We'd prefer to avoid failure later on in do_munmap:
253          * which may split one vma into three before unmapping.
254          */
255         if (mm->map_count >= sysctl_max_map_count - 3)
256                 return -ENOMEM;
257 
258         /*
259          * Advise KSM to break any KSM pages in the area to be moved:
260          * it would be confusing if they were to turn up at the new
261          * location, where they happen to coincide with different KSM
262          * pages recently unmapped.  But leave vma->vm_flags as it was,
263          * so KSM can come around to merge on vma and new_vma afterwards.
264          */
265         err = ksm_madvise(vma, old_addr, old_addr + old_len,
266                                                 MADV_UNMERGEABLE, &vm_flags);
267         if (err)
268                 return err;
269 
270         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
271         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
272                            &need_rmap_locks);
273         if (!new_vma)
274                 return -ENOMEM;
275 
276         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
277                                      need_rmap_locks);
278         if (moved_len < old_len) {
279                 err = -ENOMEM;
280         } else if (vma->vm_ops && vma->vm_ops->mremap) {
281                 err = vma->vm_ops->mremap(new_vma);
282         }
283 
284         if (unlikely(err)) {
285                 /*
286                  * On error, move entries back from new area to old,
287                  * which will succeed since page tables still there,
288                  * and then proceed to unmap new area instead of old.
289                  */
290                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
291                                  true);
292                 vma = new_vma;
293                 old_len = new_len;
294                 old_addr = new_addr;
295                 new_addr = err;
296         } else {
297                 arch_remap(mm, old_addr, old_addr + old_len,
298                            new_addr, new_addr + new_len);
299         }
300 
301         /* Conceal VM_ACCOUNT so old reservation is not undone */
302         if (vm_flags & VM_ACCOUNT) {
303                 vma->vm_flags &= ~VM_ACCOUNT;
304                 excess = vma->vm_end - vma->vm_start - old_len;
305                 if (old_addr > vma->vm_start &&
306                     old_addr + old_len < vma->vm_end)
307                         split = 1;
308         }
309 
310         /*
311          * If we failed to move page tables we still do total_vm increment
312          * since do_munmap() will decrement it by old_len == new_len.
313          *
314          * Since total_vm is about to be raised artificially high for a
315          * moment, we need to restore high watermark afterwards: if stats
316          * are taken meanwhile, total_vm and hiwater_vm appear too high.
317          * If this were a serious issue, we'd add a flag to do_munmap().
318          */
319         hiwater_vm = mm->hiwater_vm;
320         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
321 
322         if (do_munmap(mm, old_addr, old_len) < 0) {
323                 /* OOM: unable to split vma, just get accounts right */
324                 vm_unacct_memory(excess >> PAGE_SHIFT);
325                 excess = 0;
326         }
327         mm->hiwater_vm = hiwater_vm;
328 
329         /* Restore VM_ACCOUNT if one or two pieces of vma left */
330         if (excess) {
331                 vma->vm_flags |= VM_ACCOUNT;
332                 if (split)
333                         vma->vm_next->vm_flags |= VM_ACCOUNT;
334         }
335 
336         if (vm_flags & VM_LOCKED) {
337                 mm->locked_vm += new_len >> PAGE_SHIFT;
338                 *locked = true;
339         }
340 
341         return new_addr;
342 }
343 
344 static struct vm_area_struct *vma_to_resize(unsigned long addr,
345         unsigned long old_len, unsigned long new_len, unsigned long *p)
346 {
347         struct mm_struct *mm = current->mm;
348         struct vm_area_struct *vma = find_vma(mm, addr);
349         unsigned long pgoff;
350 
351         if (!vma || vma->vm_start > addr)
352                 return ERR_PTR(-EFAULT);
353 
354         if (is_vm_hugetlb_page(vma))
355                 return ERR_PTR(-EINVAL);
356 
357         /* We can't remap across vm area boundaries */
358         if (old_len > vma->vm_end - addr)
359                 return ERR_PTR(-EFAULT);
360 
361         if (new_len == old_len)
362                 return vma;
363 
364         /* Need to be careful about a growing mapping */
365         pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
366         pgoff += vma->vm_pgoff;
367         if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
368                 return ERR_PTR(-EINVAL);
369 
370         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
371                 return ERR_PTR(-EFAULT);
372 
373         if (vma->vm_flags & VM_LOCKED) {
374                 unsigned long locked, lock_limit;
375                 locked = mm->locked_vm << PAGE_SHIFT;
376                 lock_limit = rlimit(RLIMIT_MEMLOCK);
377                 locked += new_len - old_len;
378                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
379                         return ERR_PTR(-EAGAIN);
380         }
381 
382         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
383                 return ERR_PTR(-ENOMEM);
384 
385         if (vma->vm_flags & VM_ACCOUNT) {
386                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
387                 if (security_vm_enough_memory_mm(mm, charged))
388                         return ERR_PTR(-ENOMEM);
389                 *p = charged;
390         }
391 
392         return vma;
393 }
394 
395 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
396                 unsigned long new_addr, unsigned long new_len, bool *locked)
397 {
398         struct mm_struct *mm = current->mm;
399         struct vm_area_struct *vma;
400         unsigned long ret = -EINVAL;
401         unsigned long charged = 0;
402         unsigned long map_flags;
403 
404         if (offset_in_page(new_addr))
405                 goto out;
406 
407         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
408                 goto out;
409 
410         /* Ensure the old/new locations do not overlap */
411         if (addr + old_len > new_addr && new_addr + new_len > addr)
412                 goto out;
413 
414         ret = do_munmap(mm, new_addr, new_len);
415         if (ret)
416                 goto out;
417 
418         if (old_len >= new_len) {
419                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
420                 if (ret && old_len != new_len)
421                         goto out;
422                 old_len = new_len;
423         }
424 
425         vma = vma_to_resize(addr, old_len, new_len, &charged);
426         if (IS_ERR(vma)) {
427                 ret = PTR_ERR(vma);
428                 goto out;
429         }
430 
431         map_flags = MAP_FIXED;
432         if (vma->vm_flags & VM_MAYSHARE)
433                 map_flags |= MAP_SHARED;
434 
435         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
436                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
437                                 map_flags);
438         if (offset_in_page(ret))
439                 goto out1;
440 
441         ret = move_vma(vma, addr, old_len, new_len, new_addr, locked);
442         if (!(offset_in_page(ret)))
443                 goto out;
444 out1:
445         vm_unacct_memory(charged);
446 
447 out:
448         return ret;
449 }
450 
451 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
452 {
453         unsigned long end = vma->vm_end + delta;
454         if (end < vma->vm_end) /* overflow */
455                 return 0;
456         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
457                 return 0;
458         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
459                               0, MAP_FIXED) & ~PAGE_MASK)
460                 return 0;
461         return 1;
462 }
463 
464 /*
465  * Expand (or shrink) an existing mapping, potentially moving it at the
466  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
467  *
468  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
469  * This option implies MREMAP_MAYMOVE.
470  */
471 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
472                 unsigned long, new_len, unsigned long, flags,
473                 unsigned long, new_addr)
474 {
475         struct mm_struct *mm = current->mm;
476         struct vm_area_struct *vma;
477         unsigned long ret = -EINVAL;
478         unsigned long charged = 0;
479         bool locked = false;
480 
481         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
482                 return ret;
483 
484         if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
485                 return ret;
486 
487         if (offset_in_page(addr))
488                 return ret;
489 
490         old_len = PAGE_ALIGN(old_len);
491         new_len = PAGE_ALIGN(new_len);
492 
493         /*
494          * We allow a zero old-len as a special case
495          * for DOS-emu "duplicate shm area" thing. But
496          * a zero new-len is nonsensical.
497          */
498         if (!new_len)
499                 return ret;
500 
501         down_write(&current->mm->mmap_sem);
502 
503         if (flags & MREMAP_FIXED) {
504                 ret = mremap_to(addr, old_len, new_addr, new_len,
505                                 &locked);
506                 goto out;
507         }
508 
509         /*
510          * Always allow a shrinking remap: that just unmaps
511          * the unnecessary pages..
512          * do_munmap does all the needed commit accounting
513          */
514         if (old_len >= new_len) {
515                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
516                 if (ret && old_len != new_len)
517                         goto out;
518                 ret = addr;
519                 goto out;
520         }
521 
522         /*
523          * Ok, we need to grow..
524          */
525         vma = vma_to_resize(addr, old_len, new_len, &charged);
526         if (IS_ERR(vma)) {
527                 ret = PTR_ERR(vma);
528                 goto out;
529         }
530 
531         /* old_len exactly to the end of the area..
532          */
533         if (old_len == vma->vm_end - addr) {
534                 /* can we just expand the current mapping? */
535                 if (vma_expandable(vma, new_len - old_len)) {
536                         int pages = (new_len - old_len) >> PAGE_SHIFT;
537 
538                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
539                                        vma->vm_pgoff, NULL)) {
540                                 ret = -ENOMEM;
541                                 goto out;
542                         }
543 
544                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
545                         if (vma->vm_flags & VM_LOCKED) {
546                                 mm->locked_vm += pages;
547                                 locked = true;
548                                 new_addr = addr;
549                         }
550                         ret = addr;
551                         goto out;
552                 }
553         }
554 
555         /*
556          * We weren't able to just expand or shrink the area,
557          * we need to create a new one and move it..
558          */
559         ret = -ENOMEM;
560         if (flags & MREMAP_MAYMOVE) {
561                 unsigned long map_flags = 0;
562                 if (vma->vm_flags & VM_MAYSHARE)
563                         map_flags |= MAP_SHARED;
564 
565                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
566                                         vma->vm_pgoff +
567                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
568                                         map_flags);
569                 if (offset_in_page(new_addr)) {
570                         ret = new_addr;
571                         goto out;
572                 }
573 
574                 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
575         }
576 out:
577         if (offset_in_page(ret)) {
578                 vm_unacct_memory(charged);
579                 locked = 0;
580         }
581         up_write(&current->mm->mmap_sem);
582         if (locked && new_len > old_len)
583                 mm_populate(new_addr + old_len, new_len - old_len);
584         return ret;
585 }
586 

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